The complexity of the plasma proteome is extraordinary, and unlocking its secrets is considered one of the great challenges of modern day science. There is broad scientific belief that the plasma proteome is made up of many thousands of proteins, only about 2,000 of which have been detected. Of the detected proteins, the most abundant is albumin, which accounts for about one half of all plasma proteins. The top twenty most abundant proteins account for around ninety nine percent of all plasma proteins, while the remaining thousands of plasma proteins are in low-abundance, and amount to only about one percent of all the plasma proteins in total. An example of this vast dynamic range is the protein interleukin-6; for each interleukin-6 protein there are about ten billion albumin proteins. As such, it is extremely challenging to detect and measure proteins as low in abundance as interleukin-6.
Immunoglobulins are equipped with affinity receptors that are capable of capturing low abundance proteins in spite of the high complexity of the proteome. Affinity receptors capture molecules on the basis of their affinity; unfortunately, affinity is not binary—affinity is continuous. Accordingly, affinity receptors are not specific. As such, while targeted low abundance proteins are captured by affinity receptors, many other proteins get captured with them. Instead of purifying the targets, affinity receptors merely enrich their targets.
Beyond affinity receptor lack of specificity, isolation platforms utilized for affinity receptors are highly susceptible to non-specific binding of high abundant proteins through their near-universal use of surfaces. Most proteins have surfaces with hydrophobic and static electric charge characteristics that tend to make them “sticky” to other surface types. Nearly all isolation platforms use surfaces that attract high quantities of high abundance sticky proteins.
Sticky surfaces and unspecific affinity receptors create very high barriers to purification. Without ready purification capability, low abundance proteins continue to hide deep down in the largely unexplored depths of the plasma proteome.
Mass spectrometry is, perhaps, the most powerful detection platform for proteins. Its high specificity detection capabilities are universal for nearly any protein. But, because of mass spectrometry's need for enrichment or purification, these significant detection capabilities are largely unused for exploring the depths of the plasma proteome. Lacking sufficiently effective enrichment or purification methods, this powerful detection tool is not widely used to explore the depths of the plasma proteome.
Therefore, there is a strong need for a protein purification device, system and method for isolating low-abundance peptides, such as those found within the plasma proteome. The present invention satisfies this need.